Stimulation Of Subcortical White Matter Research Articles

Surgical treatment of insular tumours with tractography, functional magnetic resonance imaging, transcranial electrical stimulation and direct subcortical stimulation support

Background and purposeSurgical treatment of insular tumours carries significant risks of limb paresis or speech disturbances due to their localization. The development of intraoperative neuromonitoring techniques that involve evoked motor potentials induced via both direct and transcranial cortical electrical stimulation as well as direct subcortical white matter stimulation, intraoperative application of preoperative tractography and functional magnetic resonanceimaging (fMRI) in conjunction with neuronavigation resulted in significant reduction of postoperative disabilities that enabled widening of indications for surgical treatment. The aim of this study was to present the authors’ own experience with surgical treatment of insular gliomas. Material and methodsOur cohort comprises 30 patients with insular gliomas treated at the Department of Neurosurgery in Sosnowiec. Clinical symptoms included sensorimotor partial seizures in 86.6%; generalized seizures in 23.3%; persistent headaches in 16.6% and hemiparesis in 6.6%. All the patients were operated on with intraoperative neuromonitoring that included transcranial cortical stimulation, direct subcortical white matter stimulation as well as tractography and fMRI concurrently with neuronavigation. The analysis included postoperative neurological evaluation along with the assessment of the radicalism of resection evaluated based on postoperative MRI. ResultsPostoperatively, four patients had permanent hemiparesis (13.3%); importantly, two out of those patients had preoperative deficits (6.6%). Persistent speech disturbances were present in four patients (13.3%). Partial sensorimotor seizures were noted in two patients (6.6%). Seizures in the other patients receded. Intraoperative transcranial electrical stimulation as well as direct subcortical white matter stimulation along with tractography (DTI) and fMRI facilitated gross total resection of insular gliomas in 53.5%, subtotal in 13.3% and partial resection in 33.1%. ConclusionsImplementation of TES, direct subcortical white master stimulation, DTI and fMRI into the management protocol of the surgical treatment of insular tumours resulted in total and subtotal resections in 66% of cases with permanent motor disability in 6.6% of patients. Poor prognosis for independent living after surgery mainly affects patients with WHO grade III or IV.

Harvey Cushing’s contributions to motor mapping: 1902–1912

This review examined Dr. Harvey Cushing’s cases in the surgical records of Johns Hopkins Hospital, from 1896 to 1912. 41 patients who underwent cortical stimulation for intra-operative motor mapping were selected for further analysis. We demonstrate that Cushing used cortical stimulation to define primary motor and sensory cortices in the treatment of tumors, trauma, and epilepsy, within adult and pediatric populations. In addition, he performed stimulation of sub-cortical white matter during 4 of these surgeries, setting the stage for contemporary use of this technique in improving post-operative outcomes. This review of Cushing’s early intra-operative motor mapping illuminates his contributions, and clarifies his influence on the evolution of cortical mapping from an experimental technique to a staple of contemporary neurosurgery.

Fiber-tracking does not accurately estimate size of fiber bundle in pathological condition: initial neurosurgical experience using neuronavigation and subcortical white matter stimulation

The fiber-tracking method enables in vivo visualization of the white matter tracts of the brain using a diffusion tensor MR imaging technique. While this method represents a promising tool in the field of neurosurgery, especially when confronted with brain tumors in eloquent areas, its reliability remains unknown. We present here our preliminary validation of tractography in human subjects harboring brain tumors by comparing the results produced by neuronavigation and electrical white matter stimulation in two patients with gliomas in the eloquent area. Although we were able to visualize the pyramidal tract with the fiber-tracking technique, the images failed to present the actual size of the fiber bundles. Here we discuss the advantages and limitations of fiber-tracking in the field of neurosurgery.

Enhancement of N-methyl- D-aspartate receptor-mediated excitatory postsynaptic potentials in the neostriatum after methamphetamine sensitization. An in vitro slice study.

It has been suggested that behavioral methamphetamine sensitization involves changes in cortical excitatory synaptic inputs to neostriatal (Str) projection neurons. To test this, we performed blind whole-cell recording of medium spiny neurons in Str slice preparations. In Str neurons of naive rats, the amplitude of the subcortical white matter stimulation-induced N-methyl- D-aspartate receptor-mediated excitatory postsynaptic potentials (NMDA-EPSPs) was decreased upon hyperpolarization, owing to the voltage-dependent Mg(2+) blockade of NMDA receptor channels. In contrast, the amplitude of the NMDA-EPSPs in Str neurons of rats undergoing methamphetamine withdrawal (MW) did not show the Mg(2+) blockade and was nearly voltage independent over the membrane potential range of -70 to -110 mV. Application of the specific protein kinase C (PKC) activator, phorbol 12, 13- DL-acetate, blocked the voltage-dependent Mg(2+) blockade of NMDA receptor channels in Str neurons of naive rats. Application of the specific activator of cAMP-dependent protein kinase A (PKA), Sp-cAMPS-triethylamine salt, increased the amplitude of the NMDA receptor-mediated EPSPs at the rest but not at hyperpolarized potentials. Coapplication of the PKC and PKA activators yielded NMDA-EPSPs similar to those seen in Str neurons of MW rats. In Str slices of naive rats, tetanic subcortical white matter stimulation induced long-term depression of field potentials. In Str slices treated with the PKC and/or PKA, the same stimulation induced long-term potentiation of field potentials similar to those observed in slices obtained from MW rats. These results suggest that the enhancement of the NMDA receptor-mediated corticostriatal synaptic transmission plays an important role in behavioral methamphetamine sensitization. This enhancement is probably associated with phosphorylation of NMDA receptors mediated by the simultaneous activation of PKC and PKA.

Expression of N-methyl- d-aspartate receptor-dependent long-term potentiation in the neostriatal neurons in an in vitro slice after ethanol withdrawal of the rat

To examine changes in corticostriatal synaptic transmission in rats with ethanol withdrawal syndrome, intracellular and extracellular responses to subcortical white matter stimulation were recorded in neostriatal slice preparations. The resting membrane potential, input resistance and depolarizing postsynaptic potentials to single cortical white matter stimulation were similar in the neostriatum of naive and ethanol withdrawal rats. Repetitive stimulation of the white matter induced more pronounced N-methyl- d-aspartate receptor-mediated postsynaptic potentials in ethanol withdrawal than naive rat neostriatum. In intracellular recording, tetanic stimulation (50 Hz, 20 s) induced more pronounced post-tetanic potentiation of depolarizing postsynaptic potentials in the neostriatum of ethanol withdrawal than naive rats. However, in extracellular recording, tetanic stimulation induced smaller post-tetanic depression of population spikes in the neostriatum of ethanol withdrawal than naive rats. Tetanic stimulation of the subcortical white matter induced long-term potentiation of postsynaptic potentials and population spikes in the ethanol withdrawal rat neostriatum, while long-term depression was evoked in the naive rat neostriatum. The induction of long-term potentiation was blocked by d-2-amino-5-phosphonovaleric acid or 7-chlorokynurenic acid, N-methyl- d-aspartate receptor antagonists, but not by ( RS)-methyl-4-carboxyphenyl-glycine, a metabotropic glutamate receptor antagonist. Dopamine also significantly depressed the induction of long-term potentiation in ethanol withdrawal rat neostriatum and this depressant effect was antagonized by the D 2 antagonist l-sulpiride but not by the D 1 antagonist SCH23390. These results indicate that the N-methyl- d-aspartate component of the corticostriatal glutamatergic responses, which might be necessary for induction of long-term potentiation, was enhanced in ethanol withdrawal rats. The depression of long-term potentiation induction by activation of D 2 receptor suggests that corticostriatal N-methyl- d-aspartate response or intracellular mechanisms involving in the induction of the long-term potentiation can be suppressed by D 2 activation and that the D 2 effects are inhibited in the neostriatum of ethanol withdrawal rats.

NMDA depolarizations and long-term potentiation are reduced in the aged rat neocortex

N-Methyl- d-aspartate (NMDA) responses were recorded intracellularly in layer V neocortical neurons in in vitro slices taken from young (4–6 months) and aged (27–29 months) Fischer 344 rats. Increasing amounts of NMDA produced membrane depolarizations in both groups of cells. The regression analysis showed significantly reduced sensitivity to NMDA in old neurons compared to young. A significant long-term potentiation of the field potential evoked by subcortical white matter stimulation was present in young but not in old slices. These results suggest that aging results in a decreased sensitivity to NMDA and impaired synaptic plasticity in the neocortex.

Organization of cortical afferent and efferent pathways in the white matter of the rat visual system

Fibers forming reciprocal connections between the dorsal lateral geniculate nucleus and primary visual cortex run in separate tracts in the white matter. The corticofugal fibers are organized into bundles which project through the coronal plane at an oblique angle. We have examined the organization of corticofugal fiber tracts within the white matter of the rat using cortical slices which encompassed the predicted trajectory of these fiber bundles. Field potentials were evoked in layer VI of visual cortex by focal stimulation of subcortical white matter using microbipolar electrodes. Two major responses were elicited: a short-latency and a longer-latency response. The short-latency response was elicited in the superficial strata of white matter with proximal stimulation sites and was obtained in deeper strata for more distant, lateral sites. The longer-latency response was associated with superficial strata in white matter at both proximal and distant stimulation sites. Based on the electrophysiological properties and the white matter location for eliciting these responses, it is likely that the short-latency response is due to antidromic activation of corticogeniculate fibers, whereas the longer-latency response probably arises from orthodromic activation of geniculocortical fibers. These findings provide an electrophysiological demonstration that cortical afferent and efferent pathways are segragated within the white matter and that they can be selectively activated by focal stimulation. The fact that the fiber bundle model successfully predicted the trajectory of corticofugal fibers provides additional support for this model of white matter organization.A double labeling technique which combined orthograde axonal transport and neuronal degeneration was used to examine the topographic arrangement of corticofugal fibers in the white matter. Corticofugal fibers are topographically organized in subcortical white matter in a manner which reflects the location of their cell bodies in cortex. Fibers arising from neurons situated laterally and rostrally in the cortex are superficial to those originating from more medial and caudal neurons.This topographic ordering of fibers in the white matter suggests that contact guidance may play an important role during axonogenesis in directing corticofugal axons to appropriate subcortical targets.

The deafferented reticular thalamic nucleus generates spindle rhythmicity.

The hypothesis that nucleus reticularis thalami (RE) is the generator of spindle rhythmicity during electroencephalogram (EEG) synchronization was tested in acutely prepared cats. Unit discharges and focal waves were extracellularly recorded in the rostral pole of RE nucleus, which was completely disconnected by transections from all other thalamic nuclei. In some experiments, additional transections through corona radiata created a triangular island in which the rostral RE pole survived with the caudate nucleus, putamen, basal forebrain nuclei, prepyriform area, and the adjacent cortex. Similar results were obtained in two types of experiments: brain stem-transected preparations that exhibited spontaneous spindle sequences, and animals under ketamine anesthesia in which transient spindling was repeatedly precipitated during recording by very low doses of a short-acting barbiturate. Both spindle-related rhythms (7- to 16-Hz waves grouped in sequences that recur with a rhythm of 0.1-0.3 Hz) are seen in focal recordings of the deafferented RE nucleus. The presence of spindling rhythmicity in the disconnected RE nucleus contrasts with total absence of spindles in cortical EEG leads and in thalamic recordings behind the transection. Oscillations within the same frequency range as that of spontaneous spindles can be evoked in the deafferented RE nucleus by subcortical white matter stimulation. In deafferented RE cells, the burst structure consists of an initially biphasic acceleration-deceleration pattern, eventually leading to a long-lasting tonic tail. Quantitative group data show that the burst parameters of disconnected RE cells are very similar to those of RE neurons with intact connections. In the deafferented RE nucleus, spike bursts of RE neurons recur periodically (0.1-0.3 Hz) in close time-relation with simultaneously recorded focal spindle sequences. The burst occurrence of deafferented RE cells is greatly reduced after systemic administration of bicuculline. The preservation of both spindle-related rhythms in the disconnected RE nucleus, together with our recent experiments showing abolition of spindle oscillations in thalamic nuclei after lesions of RE nucleus (24), demonstrate that RE nucleus is the generator of spindle rhythms.

CORTICO-PYRAMIDAL INFLUENCES ON THALAMIC SOMATOSENSORY TRANSMISSION IN THE CAT

1. The effects of electrical stimulation of the pericruciate cortex on individual neurons of the ventrobasal complex (VB) of the thalamus has been studied in cats. Extracellular recording was via glass micropipettes. Unit spikes were evoked by single test shocks applied either to peripheral nerves or to the medial lemniscus.2. About half the neurons tested were excited antidromically by single shocks to restricted areas of the postcruciate cortex. Similar stimulation caused trans-synaptic excitation in about one third of the neurons.3. When these and adjacent areas of postcruciate cortex were weakly stimulated prior to the medial lemniscal test shock, the VB unit was commonly inhibited. The inhibitory effect usually lasted 300 msec. or more.4. Some VB neurons were excited by stimulation of the ipsilateral pyramid at the ponto-bulbar border. The specificity of this pyramidal stimulation was checked by monitoring antidromically evoked cortical potentials.5. Twenty-two to 30 days following cortical ablation, with degenera tion of the descending pyramidal fibers, stimulation of the exposed subcortical white matter had an antidromic inhibitory effect on the VB neurons. No transsynaptic excitation was produced in these cases either by stimulation of subcortical white matter or the medullary pyramid.6. These results suggest that some axon collaterals of pyramidal tract fibers project to the VB complex and produce excitation of small groups of VB neurons, which in turn results in inhibition of surrounding VB neurons. Possible functional significance of the results was briefly discussed.